74 AS1PHONIBRANCHIATA. 



testaceous part of the Ocythbe, and that the broad membranes 

 which in some representations have been artificially placed as 

 sails, are naturally bent backwards over the shell like the mantle 

 of some other molluscs. The interesting experiments of Madame 

 Power, in the Mediterranean, have contributed very materially 

 to lead the investigations of Naturalists to a satisfactory con- 

 clusion. This lady kept a cage under water, in which Argonautse 

 were bred in great numbers, giving her an opportunity of tracing 

 the gradual development of the shell in all its stages, from the 

 elastic and transparent nucleus to the full grown " Paper Sailor." 

 Fig. 485. 



ARIANTA. Leach. A sub-genus of land shells, containing Helix 

 arbustorum, Auct. (Gray, Turton, p. 137.) 



ARION. A genus of slugs which have no shells. 



ARROW-HEADS. One of the names by which fossils of the genus 

 Belemnites were formerly known. 



ARTEMIS. A genus of bivalve shells, distinguished from those of 

 the genus Venus, by having a rounded, denticular form, and a 

 deep, angular sinus in the palleal impression. This does not 

 appear to me to be a sufficient ground of generic distinction, the 

 palleal impressions of the Veneres being subject to great varia- 

 tions. British, also from West Indies, South America, Australia, 

 &c. A.' lincta, fig. 118. 



ARTICULATED. (Jointed.) Applied to distinct parts of shells, 

 which are fitted or jointed into each other, as the valves of 

 Chitones and those of Balani. The operculum of Nerita is said to 

 be articulated to the columella, having a small process by which 

 it is as it were locked under the edge. See Introduction. The 

 word is also applied to the Cirri, which protrude from the oral 

 openings of Cirripedes. 



ARTICULINA. D'Orb. A genus of microscopic Foraminifera. 



ASIPHON1BRANCHIATA. Bl. The second order of Paracephalo- 

 phora Dioica, Bl. Consisting of spiral univalves, which have no 

 notch or canal at the anterior part of the aperture. This order is 

 divided into the families Goniosomata, Cricosomata, Ellipsosto- 

 mata, Hemicyclostomata, and Oxystomata. 



